Applications; Pid Regulator Application - WEG CFW700 Manual Del Usuario

Keypad (HMI) and Basic Programming

4.2 APPLICATIONS

The CFW700 has some features that allow better matching the inverter commands to the
application. These features were grouped into a set of applications and can be as simple as the
forward and reverse command, or more elaborated such as a PID controller.The applications
were implemented using the SoftPLC function, in other words, ladder programming applicative
built-in to the CFW700 inverter. It allows the user that has the WLP and the built-in implemented
applicative to change it and use it as an user applicative.
Parameter P1003 allows selecting an application and uploading it to the CFW700. The CFW700
has following applications built-in:
PID Regulator.
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Electronic Potentiometer (E.P.).
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Multispeed.
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3-Wire Start/Stop.
„
Forward/Reverse Run.
„

4.2.1 PID Regulator Application

The CFW700 has the PID REGULATOR application that can be used to control a closed loop
process. This application sets proportional, integral and derivative regulator superimposed to
the regular speed control of the CFW700 inverter.
The CFW700 will compare the setpoint with the process variable and control the motor speed
trying to eliminate any error and keeping the process variable equal to the setpoint. The setting
of the P, I and D gains determines how fast the inverter will respond to eliminate this error.
Application examples:
Flow control or pressure in a pipe system.
„
Temperature of a furnace or oven.
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Dosing of chemicals in tanks.
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The following example defines the terms used by the PID controller.
A pump used in a water pumping system where is necessary to control the pressure of the
pipe. A pressure transducer is installed in the pipe and supplies an analog feedback signal
to the CFW700, which is proportional to the water pressure. This signal is called the process
variable, and can be visualized at the parameter P1012. A setpoint is programmed in the
CFW700 via keypad (P1025), through an analog input (such as a 0-10 V or 4-20 mA signal) or
via communication network. The setpoint is the desired water pressure value that the pump is
supposed to produce, regardless of the consumption variations at the pump output at any time.
It is necessary to set the parameter P0221 or P0222 to 7=SoftPLC for the operation of the PID
Regulator application.
Definitions:
The Function 1 of the Application at parameters P0231 or P0236 represents the value of the
„
PID Setpoint.
The Function 2 of the Application at parameters P0231 or P0236 represents the value of the
„
PID Feedback.
The Function 1 of the Application at parameters P0251 or P0254 represents the value of the
„
PID Setpoint.
22 | CFW700